1. Field of the Invention
The present invention relates to a manipulating device operating in two directions for the motion of work pieces between desired positions within a plane and adapted in particular for the loading and unloading of planar magazines.
2. Brief Description of the Background of the Invention Including Prior Art
Manipulating devices are known in various configurations. For example, such a manipulating device is taught in "wt Zeitschrift fur industrielle Fertigung 71 (1981) 141-145". This device is movable in the direction of two axes and comprises as a core piece a slide, which is guided on two parallel round rods in horizontal direction in two correspondingly adapted bores of the slide. The round rods are attached at their ends to portal columns of a spacially fixed position frame. A toothed gear rack runs parallel to the round rods, into which a pinion engages at the end of the drive shaft of a drive motor disposed at the slide for providing a horizontal motion of the slide.
In addition, two parallel vertical bores are provided in the slide each of which guiding a vertical round rod. The lower ends of the vertical round rods are united in an end plate, at which a gripper for the work piece is disposed. This unit (round rods, end plate, gripper, and work piece) can be moved up and down relative to the slide by way of a second drive motor cross-attached to the slide and provided with a pinion, which engages a vertically disposed gear rack connected to the end plate. Optical pulse generators are provided at the inner end of the drive motors as position sensing systems for controlling the motions of the gripper within the work area defined by the dimensions of the round rods and of the toothed gear racks. The drive motors are controlled by the pulses from the pulse generators preferably via a computing unit such that the work piece adopts the position predetermined in each case. Electromagnetical brakes are provided at the drive motors in order to avoid overdriving and to secure the work piece once the desired position is reached.
This known device is associated with the following disadvantages:
Inaccuracies in the positioning result from the flanging of the pulse generator of the position measuring system to the drive motor and the ensuing transfer of the backlash of its gear play onto the pulse generator. PA1 The error caused by the play between the pinion and the gear rack is added to the inaccuracies. PA1 The slide is produced by cutting and therefor comprises a considerable mass. PA1 The mass is increased by the braking of the drive units and the required driving power is increased. PA1 The drive motor is loaded by the weight of the parts movable in a vertical direction and this renders exact positioning more difficult.